Laboratory and semi-field evaluation of long-lasting insecticidal nets against leishmaniasis vector, Phlebotomus (Phlebotomus) duboscqi in Kenya

Abstract

Background & objectives: Phlebotomine sandflies are vectors of leishmaniases and other diseases. Long-lasting insecticidal nets (LLINs) as possible tools for control have not been widely tested against them. The objective of this study was to determine the efficacy of Olyset Net and PermaNet LLINs alongside a local brand, K-O Tab treated net (Supanet) against Phlebotomus duboscqi female sandflies.

Methods: Four replicates of unwashed and 20x washed Olyset Nets and PermaNets, K-O Tab-treated and untreated Supanet and 'no net' treatments were evaluated against sandflies within the laboratory by tunnel tests and in semi-field conditions in the greenhouse model for their efficacy.

Results: All bednets allowed entry of P. duboscqi sandflies and subsequent blood-feeding. Olyset net's blood feeding inhibition was significantly higher than that of Supanet in the laboratory but not in semi-field condition. Of the LLINs, only Olyset net had sandflies that could not feed significantly more than those of Supanet. Additionally, no significant efficacy difference was observed between LLINs washed 20x and unwashed ones. The only significant difference noted in number of sandflies that were found dead or paralyzed within bednets in the semi-field condition was between Olyset and K-O Tab treated Supanet. In the laboratory, unwashed Olyset had a significantly higher number of sandflies killed than all other bednet treatments.

Conclusion: Olyset net use in areas where sandflies are nuisance biters and/or disease vectors could be more beneficial in preventing sandfly bites than other tested bednets. It is recommended that mesh sizes of LLINs should be smaller for control of sandflies than those used for control of mosquitoes.